Advice on supporting 13 year old daughter

Hi, apologies if there are numerous threads like this, I started looking through but got distracted.

I'd really welcome advice on how to support my 13 year old DD through her Grandad's (my DF) imminent death.

He was diagnosed in January with advanced spinal & liver cancer. He'd previously been really fit & active so it's been really hard seeing him lose mobility & independence. Despite that sadness, we've had a beautiful few months with him, making the most of our time together as a family, and ensuring he knows how much we love him.

My DD is a very sensitive, mature girl, and up until this had always been willing & able to articulate & share her feelings. However, I think that as his death draws closer, she seems to have become more withdrawn. She doesn't want to talk about the situation, and just gives me a curt "I'm fine" when I ask how she's doing. I'm trying not to pressure her into talking, but am worried as I've found her crying in her room a couple of times. She stops when I try to comfort/talk to her. I'm aware she might be trying to protect my feelings but I've tried to gently explain that though I'm sad, I'm OK, and I want to be there for her.

Do people who have also been through similar things think that this is just a normal way of coping, given her age? Should I just let her be and handle it in her own way? I want her to be free to express herself however she chooses, but I'd hate the thought of leaving her alone if she's struggling?

Jammie, just in case you revisited this I wanted to thank you again for your response (I haven't posted often & rarely get any replies, so I do thank you for bothering!)

Also wanted to let you know that my DD initiated a conversation tonight. I think she told me the answer to what I'd been worried/uncertain about. She said she thought she could handle her own emotions but was concerned about the rest of the family 😍

God love her, she's so considerate!

I feel hugely relieved. This explains the quietness. She chatted unprompted for a while tonight, it was lovely.